Contribution of numerical modelling to design oxygen electrode for micro-solid oxide cells: A case study of high-performance nano-columnar La2NiO4 thin films

This article presents a numerical study that aims to guide the development of nano-columnar La2NiO4 thin films as high performing oxygen electrodes for micro-Solid Oxide Cell (mu SOC). La2NiO4 thin films were deposited by Pulsed Injection Metal Organic Chemical Vapor Deposition (PI-MOCVD) and their performance is characterized by Electrochemical Impedance Spectroscopy (EIS) and Electrical Conductivity Relaxation (ECR). Excellent performance is obtained for 1 mu m thick film with an Area Specific Resistance (ASR) of 0.12 0 cm2 at 600 degrees C, making them suitable for low-temperature mu SOCs. A Finite Element Method (FEM) model has been implemented and used to predict the ASR and impedance spectra in order to guide further optimization of the film thickness and morphology. After experimental validation of the model using various electrode thicknesses, the optimal value is estimated to be between 3 and 4 mu m for the temperature range of 450-650 degrees C. For each temperature and thickness, the model can clearly predict whether the electrode is limited by the surface exchange reactions or the bulk diffusion. The simulations revealed that the gas diffusion process is not rate-limiting when the electrode thickness is below 5 mu m and the temperature is below 650 degrees C. Furthermore, a geometrical parameters analysis study allowed to determine the ideal nano-columnar morphology for this promising electrode composition.